[service I created].service: Failed to execute command: Permission denied

Solution 1:

Just installed writefreely on an Ubuntu 18.04 test machine following your guide without problem:

$ sudo journalctl  -u writefreely
-- Logs begin at Thu 2020-04-09 20:43:07 UTC, end at Thu 2020-04-09 21:57:13 UTC. --
Apr 09 21:57:00 ubuntu systemd[1]: Started WriteFreely Instance.
Apr 09 21:57:00 ubuntu writefreely[1435]: 2020/04/09 21:57:00 Starting WriteFreely 0.11.2...
Apr 09 21:57:00 ubuntu writefreely[1435]: 2020/04/09 21:57:00 Loading config.ini configuration...
Apr 09 21:57:00 ubuntu writefreely[1435]: 2020/04/09 21:57:00 Loading templates...
Apr 09 21:57:00 ubuntu writefreely[1435]: 2020/04/09 21:57:00 Loading pages...
Apr 09 21:57:00 ubuntu writefreely[1435]: 2020/04/09 21:57:00 Loading user pages...
Apr 09 21:57:00 ubuntu writefreely[1435]: 2020/04/09 21:57:00 Loading encryption keys...
Apr 09 21:57:00 ubuntu writefreely[1435]: 2020/04/09 21:57:00 Connecting to sqlite3 database...
Apr 09 21:57:00 ubuntu writefreely[1435]: 2020/04/09 21:57:00 Adding {domain} routes (single user)...
Apr 09 21:57:00 ubuntu writefreely[1435]: 2020/04/09 21:57:00 Going to serve...
Apr 09 21:57:00 ubuntu writefreely[1435]: 2020/04/09 21:57:00 Serving on http://localhost:8080
Apr 09 21:57:00 ubuntu writefreely[1435]: 2020/04/09 21:57:00 ---

Probably you have some other problem on your host.