I’m running lxd 4.0.2 from a snap on Debian 10 (Debian 4.19.132-1 kernel)
From reading Weekly status no 136, I think it should be using nftables (case “4” below):
It uses the following logic to pick a driver:
1 Nftables available and has a non-empty ruleset. Use nftables.
2 Nftables isn’t available. Use xtables.
3 Both nftables and xtables are available, but xtables has a non-empty ruleset. Use xtables.
4 Both nftables and xtables are available, but neither are in use. Use nftables.
From dumping the rules in use after bootup and after lxd has started, I can see: