Sql Server 2017 - Cannot shrink transaction log file, blocked by LOG_BACKUP status
The ldf file is divided into Virtual Log Files (VLFs). The last used VLF sets the limit to how small the file can be shrunk. I.e., the file can only be shrunk from the end towards the beginning. So you apparently have a used VLF towards the end of the file. You need to get un-used VLFs at the end. 

What you do is you empty the log (BACKUP LOG if not in SIMPLE mode, else the CHECKPOINT command), and then shrink. And then you do that several times. That is the key, several times. At some point in time, you will have as many un-used VLFs at the end so the file will shrink to your liking.

And then set recovery model properly (based on if you do log backups or not).

You can investigate the VLF layout using DBCC LOGINFO.