As a female engineer and someone whose range of personal interests seem (sadly) to include more men than women (competitive rifle shooting, rock band, nautical ropework, historical sailing, etc) it’s a bit hard not to have opposite-sex friends.
I have had men want to get closer than I wanted and have moved away from them. I have one very deep and genuine long-term friendship that I nonetheless “monitor” constantly for signs of less-than-platonic interest - none so far in twenty years.
So I voted “nothing intrinsically wrong”. Not everything lawful is automatically prudent but I am adamant there is nothing intrinsically wrong in it.
If anyone round here wanted to get funny about me having male friends I would a) have to say “get a job” as I am the breadwinner and it’s kinda par for the course, and b) have to point out the number of female friends Him Indoors has, and the obvious mental re-adjustment he goes through when I book male musicians for our church music/wedding/function group when that group has, funnily enough, been nearly exclusively female over the years and has provided most of our personal friends …