ryrona Android enables WireGuard support in the Generic Kernel Image configuration already but hasn't added the infrastructure for configuring it to netd, Settings, etc. yet. It would be a lot of work just to add basic functionality and a lot more work to support complex setups.
ryrona There are other apps available for managing encrypted USB devices. That's not the only option. Android only permits FAT and exFAT for external storage due to major security issues with supporting ext4, xfs, f2fs, etc. Android has an encryption format for added storage which can use ext4 or f2fs with fscrypt, but it's not for portable drives and is explicitly tied to the device in a similar way as the internal storage encryption. It's not what you want, and it's meant for a storage device which remains attached such as an sdcard since the purpose of it is offloading most data from the internal SSD. It could be slightly extended to work well with USB drives, but it's not usable for transferring files even between two Android devices.
https://source.android.com/docs/core/storage/adoptable