Not to take this as 100% authoritative answer (my memory if not of most reliable) but to get idea since I was involved in early stages of GFN sieving and prime search.
As far as I can remember, David Underbakke has n=17 reserved and is doing search in this range for couple of years. So yes, it is being done elsewhere and PrimeGrid is doing other ranges.
David found first prime for n=17 back in 2009: 386892^131072+1.
David's AthGfn64 was used for sieving and was enhanced, adjusted (PrimeGrid factoring file requirements) and optimized when used in PG's sieving. Looking into my old e-mails, that was in 2009 as well (before n=17 prime). I've done most of the initial sieving on CPUs and low n, high b (up to b<100M) primality tests using CPUs as well (in pre-GPU era).
Later, sieving was ported to CUDA GPU and GFNSvCUDA was introduced. You can imagine it was a game changer.
And later on, GeneferCUDA for PRPNet and BOINC was introduced, a major game changer.
Badge score: 1*1 + 5*1 + 8*3 + 9*11 + 10*1 + 11*1 + 12*3 = 186