Betting on friendly matches is both risky and profitable if analyzed correctly, it's true that when a favorite team plays a friendly, they usually won't field their main players, but for the other team or opponent, especially if that team, club or country is a low-ranked team or an underdog, they will act as if it's not a friendly. This will be profitable if you have the courage to choose the underdog team in your bet because the odds from the bookmaker will certainly be high, meaning you're betting against the market. If you have the skills or know the team, it's worth a try.
Yes, you can get good odds from underdogs. But to me friendly matches seem like a bit of a
trust issue type. Because a lot of things are not clear in advance who will play for how long, who will be serious, all of these things change during the match. I think the biggest problem here is consistency. What worked in one match can be completely the opposite in the next match, So betting on such matches with too much confidence seems a bit risky. You can try small things, but if you go in with high hopes, you often have to be disappointed.