H/t my friend George, the latest instance of this is the Muslim Pontic speakers, who have remained in Turkey, using Turkish orthography. Take this from romeyika.com:
Paleya temeteri i trani ontan uç eksernan alo ğlosa çe ethelenan kati na leğun t' enan t' alo, eleğan aletera çe eğriçenan aletera. Emis pa estekam çe eterenamatinus çe tipo uç eporenam n' eğrikume. Aytika esane pola ama ata pal exathan çe epiğan. Ula enespalamata. Eğo oso erthan so num çe oso eporesa na sorevo apada ce apaçi, esorepsa çe eğrapsata. Ada katu na diğo sas eliğa apata nto esorepsa çe esis pa an erxuntan so nusuna aytika, enositeta apo katu. Na min anespalkuntan çe xantane çe pane.
Some decidedly un-Turkish placement of ğ, of course, and x unapologetically for the voiceless velar fricative. And of course there's no standard in place. Wikipedia (bless) in its article on Pontic notes dh for /ð/ (and h or kh for /x/); I just saw d and x. I note one of the commenters uses ä for [æ] (like Pontic written in Greek script uses α̈), while the website admin just uses e. The Soviet (pre-Stalin) Pontians, who had a phonetic Greek script with no diacritics (so ςς was [ʃ]) had the best solution: historically and phonologically [æ] is /ia/, so they just spelled it ια, and trusted you could do the phonetics in your head.
For jollies, let's do it the way a Christian Pontian would. Only with more misaccentuations:
Παλαία τεμέτεροι οι τρανοί όνταν ουκ έξερναν άλλο γλώσσα και έθελεναν κάτι να λέγουν τ' έναν τ' άλλο, έλεγαν αλέτερα και εγροίκεναν αλέτερα. Εμείς πα εστέκαμ και ετέρεναμ ατους και τίπο ουκ επόρεναμ ν΄εγροικούμε. Αούτικα έσανε πολλά άμα ατά παλ εχάθαν και επήγαν. Ούλα ενέσπαλαμ ατα. Εγώ όσο έρθαν σο νου μ' και όσο επόρεσα να σωρεύω απαδά και απακεί, εσώρεψα και έγραψα τα. Αδά κάτου να δηγώ σας ελίγα απ' ατα ντο εσώρεψα και εσείς πα αν έρχουνταν σο νου σουνα αούτικα, ενώσητε (?) τα από κάτου. Να μην ανεσπάλκουνταν και χάντανε και πάνε.
(One thing: a Christian Pontian would say 'κ, not ουκ̌. The Ancient Greek negator has survived with all its phonemes intact only in the Of valley. And the Christian Pontian will call his ancestral language "Pontic"—a modern learnedism—and not Romeic, or as this passage does, "Different." Neither are eager to continue the old confusing habit of calling themselves Lazoi. But otherwise, the same blithe ignoring of subjunctive aspect, the same columnar stress, the same focus particles.)
Of course, there's plenty of back story to the fact that Pontic gets written in two scripts. (Cyrillic too, according to Wikipedia; I've certainly seen Mariupolitan in Cyrillic, and I have no reason to doubt it for Pontic, I just haven't seen any... Er, strike that.) The Muslim Pontians may be hospitable enough to the visiting Christian Pontians these days, but they're pretty insistent about their Muslim identity, and they won't be happy to be told that their script isn't the Real Way of writing Pontic. Which makes me wonder what will happen to the Pontic wikipedia. It's a Greek script (and Greece) affair so far, but "Start Writing in the Forum" does appear in both Greek and Turkish orthography.
I also note that the Pontic wikipedians have worked out their own diacritic lite orthography. Including dealing with the problematic [æ ø] as the non-Greekish (so non-confusable) εα εο. A bold and unfamiliar solution, which makes me uneasy—in other words, a resounding success!
But what is this I see? A Tsakonian Wikipedia? Έννι αραμού μακρζυά, όννι μπορού να γράφου γρούσσα πφ' όννι νοού...