So, apparently I missed the memo that reiser support would be removed from OpenSuSe. I have a few boot disk partitions that are ReiserFS, and naturally now I cannot boot. What is the easiest fix for this? Can I boot an older release (15.2 or so) and convert the partitions to btrfs, or is there a more straight forward way to fix this (otherwise I see convert to btrfs, fix the fstab, recreate initrd, sprinkle with holy water and reboot)?
Just a few remarks, not a detailed plan.
You can of course boot from a rescue medium that supports Reiserfs. Could be the 15.2 installation DVD/USB-stick (when 15.2 did support Reiserfs).
I am not sure what you mean by “convert the partitions to btrfs”, but you can not convert in place. You can create a new, large enough, file system (e.g. Btrfs or ext4) and then copy all files to it.
When you choose for Btrfs, you probably want that the same as a fresh installtion constructs it with the proper subvolumes. So you must study how to do that (or just go for ext4).
HTH.
zypper in reiserfs-kmp-default
echo "options reiserfs allow_unsupported=1" > /etc/modprobe.d/50-reiserfs.conf
mkinitrd
I have no doubt that that is the easiest way to get things running 
But I want to encourage the OP to plan the conversion ASAP after that
You probably also need user space tools
zypper in reiserfs
OK, finally back out of the mountains to work on this. zypper is apparently unavailable from the rescue boot. So, could I tar off “/” somewhere, remake the partition as btrfs then put the contents back (changing fstab)? FWIW, currently booted 15.2 rescue from a usb.
You run it after chroot into your target system. Just like mkinitrd. And you can use any live image for that, be it openSUSE, Knoppix or SystemRescueCD.
Thanks for that! But does it sound like I can tar off the contents, make the two partitions in question btrfs, replace the data and it will work? The two in question are „/„ and „/var“. I don‘t see any problem with the latter….
I suggest if you wish to migrate to BTRFS, that you tar off only user data, then do a fresh installation. Otherwise, backup, format EXT4, restore, adjust /etc/fstab and /etc/default/grub for the new UUIDs, regenerate /boot/grub2/grub.cfg.
Well, you will likely need to reinstall bootloader as well (unless /boot is already on separate partition) but yes, in principle it will work. It will involve the same chroot to recreate mkinitrd, possibly fix bootloader etc. So you could just as well fix resiserfs now and plan for migration later.
Note that in case of btrfs there is no single tool to recreate the same subvolume layout and snapper setup as done by installer. So as already suggested it may make more sense to perform new installation and then overwrite configuration files from backup.
For other filesystems like ext4 you can just copy data over.
I took the cowards way out and reinstalled. So far most of the services I need are running again (homebridge, node-red, mqtt server).
Thanks again to everyone for giving their aid and opinions.