GPU: Any supported Polaris, Vega, Navi (NOT RX6700).
Motherboard: All tested Z690 motherboard were found to work well with Alder Lake; issues are now creeping in with Z790 and BIOS revisions which add support for Raptor Lake, as manufacturers begin to diverge from Intel's reference implementation (Gigabyte is the main offender for now).
If you're buying new for an Alder Lake build, go for any Z690 board other than Gigabyte (Asus, AsRock, MSI…) and, if possible, stay with the pre-Raptor Lake BIOS. Check for your prospective motherboard in the User Builds and Golden Build threads.
Don't bother with on-board Maple Ridge. If Thunderbolt is needed, the best solution is a Gigabyte Titan Ridge card on a motherboard with a 5-pin header.