Any recommendations for 4G dongle for Raspberry Pi?

I have a Pi 4 on my boat in France.  It sends back monitoring
information like battery voltages while I'm not on the boat.

Currently it connects via a TP-Link MR200 4G router which has a
free.fr SIM in it.  This has worked OK for many years but I think the
damp must have finally got to it because last time I was on the boat
(in March) it was very flakey, I had to keep restarting the router or
even power cycling it.

I'm going out to the boat again in a few days time and I'm looking for
a quick and easy (and cheap) way to restore the connection while I
test to find out whether it's the SIM is faulty or the MR200 router.

So can anyone recommend a 4G dongle that is known to work well in a Pi
4?  Then I can put the free.fr SIM in that to see if the SIM is OK
(and there's a Free shop nearby if I need to replace it).  If the SIM
is OK then I'll know the problem is with the MR200 router and I can
replace that.

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Chris Green
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