picking up #21791, the author has stated they cannot squash.
This is a useful note to prevent any issues from being opened up about this. The reason that both cannot co-exist and build bitcoin is stated here:
... the reason is sharing /usr/local/include/ and /usr/local/lib/ directories by both qt5 and qt6 installations.
Changes from original PR:
- slightly move the note up in this section, this placement seems more appropriate to me
- drop "Note:"