Thanks for reply.
I've done RT kernel 3 years ago, works fine for me,
but now found a bug with RTS/CTS for H3 uart and need to update.
I see the latest RT patches 4.19.106, but Armbian uses 4.19.115.
Is any way to roll back Armbian to 4.19.106 ?
I'm going to check "current" branch now.