The log can be safely deleted, although it would be useful to know what exactly caused it to balloon so much. If you can, before deleting it please try to pack it (e.g. using 7-Zip) with maximum compression. If the problem is caused by the same lines repeated over and over, the file should pack to a relatively small size. If that's the case, you could then upload it for inspection.
Interesting exercise. Log on my instance is 1.70 GB. Compresses down to 36 MB.
Eyeballing, about 99pc of the lines are some variation of:
2022-03-04 13:49:10: BackOffHandler: "Plugin outline: Applying a backoff of 8 seconds due to frequent plugin API calls. Consider reducing the number of calls, caching the data, or requesting more data per call. API call was: ", "joplin.settings.value", "["h2Prefix"]", "[Wait count: 1]"