We most likely won't change that for Matomo 4 to avoid possible problems with Matomo plugins or Matomo for wordpress. We are currently preparing Matomo 5, where we might consider to also update jQuery (if it doesn't cause regressions with wordpress).
Would you mind to rebase/change your PR to target
5.x-dev or create a new PR for that if that is easier.
Wordpress already has jQuery 3.6.0 in it since 2 years ago.
They also have jQuery Migration already set. No worries for breaking.
I've already patched my Matomo 4.11.x package but file integrity checker gives back false positive error.
So matomo installation couldn't be checked for integrity because of jquery.min.js substitution.
This also is a security flaw in the system. We don't want to lower our security level in core system.
Awesome, thanks a lot!