ARM has their 'Server Base Boot Requirement' for server systems to boot from UEFI but, as you point out, their client situation is crazy fragmented.
Early adoption of UEFI by the RISC-V community (on RISC-V GitHub page & initial support landing in Linux kernel 5.10) will be very interesting to watch, particularly later this month when SiFive demos the first 'RISC-V PC'.
2020-[early]2021 is a particularly poor time to build a "future-resistant" PC. Intel has yet to ship complete systems with PCIe 4.0 support, and both Intel and AMD are expected to deliver DDR5 & USB 4.0 (Thunderbolt 3 compatible, if external I/O is a concern) platforms in late 2021 & early 2022 respectively. AMD is on its last full processor generation for its socket AM4 (perhaps we'll see a Zen 3+ in 2021, which would mean 3 full generations and 2 half-generations on the same socket), and Intel rarely supports a socket for more than 2 generations.
If going with Intel, late 2021 is the best "future-resistant" move, with early 2021 bringing only Rocket Lake-S processors (11th gen, finally moving away from the then almost 6-year-old Skylake architecture, but still on 14nm), with PCIe 4.0 but still no DDR5. Late 2021 will bring Alder Lake-S processors (12th gen & finally on 10nm SF) on a platform that will include PCIe 5.0, DDR5 & USB 4.0.
If going with AMD, early 2022 is the best "future-resistant" move, with Zen 4 processors on the [likely to be long-lived] AM5 platform bringing DDR5, USB 4.0 and likely PCIe 5.0.
It has just been discovered that research causes cancer in rats.