Latest pijul with tag support:

$ pijul tag create -m "3"
MPKFLIOZ5KYBHPLXI6LH7EIPTEI37JZ4AKLKEPJMWUKLOY6EOD6QC
$ pijul tag
Error: Not a directory (os error 20)
Tag MPKFLIOZ5KYBHPLXI6LH7EIPTEI37JZ4AKLKEPJMWUKLOY6EOD6QC
Author: [Author { name: "tankf33der", full_name: Some("Mike"), email: Some("mpech@tuta.io") }]
Date: 2021-05-09 10:21:47.306728923 UTC
State: F67CXZJ6VPYJQKJNUMMJXVLZEJFWVG6PYHGNBNKM6WGKXBOEG5OAC

    3

$ pijul tag checkout MPKFLIOZ5KYBHPLXI6LH7EIPTEI37JZ4AKLKEPJMWUKLOY6EOD6QC --to-channel m22
Error: No such file or directory (os error 2)
$ 

Done, thanks!