There are still edge cases but I can count on one hand the number of users who have run into it since Fedora switched to Btrfs by default (on desktops) two year

There are still edge cases but I can count on one hand the number of users who have run into it since Fedora switched to Btrfs by default (on desktops) two years ago (and Cloud edition in the most recent Fedora release late last year). The upstream maintainer of btrfs-progs also maintains btrfs maintenance https://github.com/kdave/btrfsmaintenance https://github.com/kdave/btrfsmaintenance which is a set of scripts for doing various tasks, one of which is a periodic filtered balance focusing on data block groups. I don't run it myself, because well (a) I haven't run into such a bug in years myself (b) I want to run into such a bug so I can report it and get it fixed. The maintenance script basically papers over any remaining issues, for those folks who are more interested in avoiding issues than bug reporting (a completely reasonable position). There's been a metric ton of work on ENOSPC bugs over the years, but a large pile were set free with the ticketed ENOSPC system quite a few years ago now (circa 2015? 2016?)