This is happening with Xdebug 3.5.3/PHP 8.3.33 on a SLES 15 SP7 system; I believe using the SUSE provided packages. The systemd private tmp path it reports in xdebug_info() and prepended to /tmp paths is incorrect and not actually the one used on the host. That is, with the mountinfo below, it reports that /tmp/systemd-private-57d3315f5ac2496098a5d7e5f2bbbea7-apache2.service-0oynxS is the path in use when the correct path to the /tmp seen by PHP outside of the process would be /tmp/systemd-private-57d3315f5ac2496098a5d7e5f2bbbea7-apache2.service-pwpfxr. The mountinfo for the process is below:

446 135 254:2 / / rw,relatime shared:326 master:1 - ext4 /dev/mapper/system-rootlv rw,discard
447 446 254:1 / /usr rw,relatime shared:352 master:2 - ext4 /dev/mapper/system-usrlv rw,discard,data=ordered
451 447 254:7 / /usr/local rw,relatime shared:353 master:82 - ext4 /dev/mapper/system-usrlocallv rw,discard,data=ordered
452 446 0:5 / /dev rw,nosuid shared:354 master:3 - devtmpfs devtmpfs rw,size=4096k,nr_inodes=4050823,mode=755,inode64
453 452 0:22 / /dev/shm rw,nosuid,nodev shared:355 master:4 - tmpfs tmpfs rw,size=43204380k,inode64
454 452 0:23 / /dev/pts rw,nosuid,noexec,relatime shared:356 master:5 - devpts devpts rw,gid=5,mode=620,ptmxmode=000
455 452 0:31 / /dev/hugepages rw,nosuid,nodev,relatime shared:357 master:16 - hugetlbfs hugetlbfs rw,pagesize=2M
456 452 0:19 / /dev/mqueue rw,nosuid,nodev,noexec,relatime shared:358 master:17 - mqueue mqueue rw
464 446 0:21 / /sys rw,nosuid,nodev,noexec,relatime shared:359 master:6 - sysfs sysfs rw
465 464 0:6 / /sys/kernel/security rw,nosuid,nodev,noexec,relatime shared:360 master:7 - securityfs securityfs rw
466 464 0:25 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime shared:361 master:8 - cgroup2 cgroup2 rw,nsdelegate,memory_recursiveprot
467 464 0:26 / /sys/fs/pstore rw,nosuid,nodev,noexec,relatime shared:362 master:9 - pstore pstore rw
489 464 0:27 / /sys/firmware/efi/efivars rw,nosuid,nodev,noexec,relatime shared:363 master:10 - efivarfs efivarfs rw
581 464 0:28 / /sys/fs/bpf rw,nosuid,nodev,noexec,relatime shared:364 master:11 - bpf bpf rw,mode=700
582 464 0:12 / /sys/kernel/tracing rw,nosuid,nodev,noexec,relatime shared:365 master:18 - tracefs tracefs rw
583 464 0:7 / /sys/kernel/debug rw,nosuid,nodev,noexec,relatime shared:366 master:19 - debugfs debugfs rw
609 583 0:12 / /sys/kernel/debug/tracing rw,nosuid,nodev,noexec,relatime shared:367 master:836 - tracefs tracefs rw
610 464 0:32 / /sys/fs/fuse/connections rw,nosuid,nodev,noexec,relatime shared:368 master:20 - fusectl fusectl rw
611 464 0:33 / /sys/kernel/config rw,nosuid,nodev,noexec,relatime shared:369 master:21 - configfs configfs rw
612 446 0:20 / /proc rw,nosuid,nodev,noexec,relatime shared:370 master:12 - proc proc rw
613 612 0:30 / /proc/sys/fs/binfmt_misc rw,relatime shared:371 master:15 - autofs systemd-1 rw,fd=34,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=17451
614 613 0:52 / /proc/sys/fs/binfmt_misc rw,nosuid,nodev,noexec,relatime shared:372 master:380 - binfmt_misc binfmt_misc rw
615 446 0:24 / /run rw,nosuid,nodev shared:373 master:13 - tmpfs tmpfs rw,size=6488004k,nr_inodes=819200,mode=755,inode64
621 615 0:47 / /run/vmblock-fuse rw,nosuid,nodev,relatime shared:375 master:215 - fuse.vmware-vmblock vmware-vmblock rw,user_id=0,group_id=0,default_permissions,allow_other
623 615 0:64 / /run/user/0 rw,nosuid,nodev,relatime shared:376 master:734 - tmpfs tmpfs rw,size=3244000k,nr_inodes=811000,mode=700,inode64
624 623 0:65 / /run/user/0/gvfs rw,nosuid,nodev,relatime shared:377 master:780 - fuse.gvfsd-fuse gvfsd-fuse rw,user_id=0,group_id=0
625 623 0:66 / /run/user/0/doc rw,nosuid,nodev,relatime shared:378 master:797 - fuse.portal portal rw,user_id=0,group_id=0
626 615 0:51 / /run/user/1500 rw,nosuid,nodev,relatime shared:379 master:502 - tmpfs tmpfs rw,size=3244000k,nr_inodes=811000,mode=700,uid=1500,gid=1500,inode64
627 446 254:3 / /boot rw,relatime shared:383 master:70 - ext4 /dev/mapper/system-bootlv rw,discard,data=ordered
628 627 254:12 / /boot/grub2/i386-pc rw,relatime shared:384 master:91 - ext4 /dev/mapper/system-boot386 rw,discard,data=ordered
629 627 254:11 / /boot/grub2/x86_64-efi rw,relatime shared:385 master:94 - ext4 /dev/mapper/system-bootx64 rw,discard,data=ordered
630 627 8:1 / /boot/efi rw,relatime shared:386 master:100 - vfat /dev/sda1 rw,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro
631 446 254:10 / /home rw,relatime shared:494 master:73 - ext4 /dev/mapper/system-homelv rw,discard,data=ordered
632 446 254:9 / /opt rw,relatime shared:510 master:76 - ext4 /dev/mapper/system-optlv rw,discard,data=ordered
633 446 254:8 / /tmp rw,relatime shared:518 master:79 - ext4 /dev/mapper/system-tmplv rw,discard,data=ordered
634 446 254:5 / /srv rw,relatime shared:520 master:85 - ext4 /dev/mapper/system-srvlv rw,discard,data=ordered
635 634 254:4 / /srv/www rw,relatime shared:521 master:97 - ext4 /dev/mapper/system-srvwwwlv rw,discard,data=ordered
636 446 254:6 / /var rw,relatime shared:522 master:88 - ext4 /dev/mapper/system-varlv rw,discard,data=ordered
637 446 254:13 / /phprepo rw,relatime shared:541 master:457 - ext4 /dev/mapper/system-phprepo_lv rw,discard,data=ordered
616 615 0:24 /systemd/inaccessible/dir /run/credentials ro,nosuid,nodev,noexec shared:381 master:13 - tmpfs tmpfs rw,size=6488004k,nr_inodes=819200,mode=755,inode64
617 615 0:24 /systemd/propagate/apache2.service /run/systemd/incoming ro,nosuid,nodev master:13 - tmpfs tmpfs rw,size=6488004k,nr_inodes=819200,mode=755,inode64
618 633 254:8 /systemd-private-57d3315f5ac2496098a5d7e5f2bbbea7-apache2.service-pwpfxr/tmp /tmp rw,relatime shared:519 master:79 - ext4 /dev/mapper/system-tmplv rw,discard,data=ordered
619 636 254:6 /tmp/systemd-private-57d3315f5ac2496098a5d7e5f2bbbea7-apache2.service-0oynxS/tmp /var/tmp rw,relatime shared:523 master:88 - ext4 /dev/mapper/system-varlv rw,discard,data=ordered

I think the fact it doesn't begin with /tmp is what trips it up; it should probably be looking for the actual mount point being /tmp?