For me it depends a bit on how accurate the romance is purporting to be. If it’s outright just enjoyable fluff I allow more leeway, if it’s touting itself as a serious, well researched piece, it better be be pretty accurate.
I can overlook some mistakes if they are minor (or just because no one wants to read about pre-modern dentistry) but if something is just factually wrong and a big part of the story I can’t get past it. This would include ignoring or changing major laws of the time or getting major historical facts wrong.
Regarding historical romance characters whose authentic lives seem to go against the laws, or the stereotypical roles of men and women at the time such as strongly feminist female characters, LGBT characters etc, I can believe they get their happily ever after if they are in a wealthy and privileged enough group.
I can think of historical examples of LGBT people who led open and pretty happy lives because they had the wealth, position and influence to do so. Whether it’s Monsieur, Louis XIV’s brother (who still had his political marriages, one a happy one) but openly dressed as he chose and had relationships and love affairs with other men or Kings and Queens of England who had their same sex lovers and favorites they were above the laws that ruled “lesser” people’s lives.
I can easily imagine a wealthy aristocrat or even a wealthy merchant class man carving out the life he wanted with his chosen lover. Bachelorhood is always something that was more respected than “spinsterhood”. The man is always the “catch” and those that didn’t marry simply avoided the “noose” of marriage. If a wealthy guy doesn’t need to provide an heir to carry on a title or dynasty he can spend his life as he chooses with whom he chooses.
To a lesser degree wealthy women had some leeway as well. If they weren’t so wealthy and connected they needed to make a great marriage and had enough money to live on, or were wealthy widows etc, they could set themselves up in a comfortable household with the companion of their choice. In “Possession” by A.S. Byatt, the poet Christabel LaMott has enough family money to set up a household rescuing poor governess Blanche and 20th century scholars studying LaMott’s work with modern eyes, realize it was a romantic relationship.
To be outside the “norm” whether it’s Mary Wollstonecraft or Lord Byron or Lady Catherine Jones means you have to have some money, friends and a certain level in society in order to break rules others have to follow.