Does not need to be wrapped at so few cols -- you can use 77 cols as in the ====== at the top

Splitting into two sentences improves clarity IMO - "...derived from OpenSSL. It is integrated..."

did not properly, were not thread-safe etc.?

Might want to have a brief comment about why ossl exists, given this last sentence.

delete

I guess for this one it is really "reboot if running a custom kernel with ossl built-in, or unload and reload the ossl kernel module"? Although perhaps it is fine to always document a reboot for kernel issues.

Remove 12.4, add patch details

Yes, I think an unconditional reboot is best, plus I believe ossl (and any other OCF module) can fail to unload if some consumer is still holding a session open.

What does that "FreeBSD 12.4" line represent?

It's there as a sample for the case where there are different patches per release, e.g.:

[FreeBSD 14.0]
# fetch ... bug.14.patch
...

[FreeBSD 13.2]
# fetcch ... bug.13.patch
...
# gpg -verfiy bug.13.patch.asc

If the same patch applies to all affected releases (or there's only one) it can be omitted.