Where can I get a history of METARs?
OgiMet Professional information about meteorological conditions in the world is such a site that offers 30-day history for METARs/SPECIs and TAFs reports.
The coverage is said to be worldwide. Here is a glance at the query interface:

The site states these conditions of use for the reports:

About all the codified met. reports (SYNOPS, METAR ...), the copyright
are from every country or source institution. To use them,
read WMO resolution 40.

(essentially it says it's free for use.)
The site accepts requests for up to 31 days at once.
Example: METARs for month of September 2020 for Orly / LFPO: