I married a man who entered the UK as an illegal immigrant. After 5 years of relationship and two years of living together, we applied for his visa on grounds that he is my ‘durable life partner’ (this was while EU law was still applicable in the UK, I’m a EU citizen with settlement status). We went via an immigration lawyer and were upfront about the fact that he entered the UK illegally (not that this could have been concealed anyway). The application was successful and he was granted pre-settled status. We then got married a couple of years later and had a child.
I will answer any questions, but might not engage in wider discussions about illegal immigration, there are enough threads about that topic and this is an AMA.