Ted Ts’o sent out the EXT4 updates today for Linux 6.11. He explained in that pull request:
“Many cleanups and bug fixes in ext4, especially for the fast commit feature. Also some performance improvements; in particular, improving IOPS and throughput on fast devices running Async Direct I/O by up to 20% by optimizing jbd2_transaction_committed().”
Note my research of BTRFS is almost a year old now. And there was still a few headlines making round of problems with BTRFS in some cases. A controlled NAS system is not the same as random user configuration of a random desktop user. And as said in my comment, I was not sure if it would be stable for my installation (when I did my research) and did not claim it to be unstable. On the other side, I know for a fact that EXT4 is stable and I did not research more or experiment to find out which one is better for me.
Current state of BTRFS: https://btrfs.readthedocs.io/en/latest/Status.html (note when I did my research, Linux was at Kernel v6.4, therefore BTRFS was in a worse situation than today)