Tl;tr : adult unrequited love, responsibility, emotional support

[Please sorry for any mistake with the language. I am no native speaking]
It’s been almost ten years since I first joined this forum... unfortunately, I’ve had another setback during the last here, and I’m back here, in this one safe space on the internet, to ask for some support

I live in Europe. Somehow always worked before, but after covid-19 and a series of personal losses, I went through a period of neglecting important areas of my life. I became unemployed, except for a brief period, struggled to get back on my feet, and had housing issues, including an unfinished home renovation and hoarding problems -recovered
Despite trying to behave well, a was broken. I am 38 now

I knew a man through an online cinema community that I -at first- mostly followed silently, without interacting much. Eventually, I was invited to a group event last December. I hadn't seen people in a long time, but still attended
Was used to single life, no casual dating, nothing... since 2018
I developed a strong interest in him from the beginning, but my personal circumstances made it difficult to express my feelings after.
I was evasive about my work situation and generally kept my distance from people.
I followed some Twitch live and Discord activitis (small group, adults) and tried to interact in bad conditions. I know

Around April or May, another woman who was already began interacting with him more frequently in private, and they eventually started dating in july. I never tried to interfere, and I've tried to accept the situation, but I still deeply regret never expressing my feelings
I had previosly met her another time in february

I've been single for eight years, and my feelings for him were sincere. I have no intention of disrupting their relationship and i have some dignity but also angry and there is more to that. In july i tried to walk away silently but the creator looked for me and ask where i had been
Eventually even when i tried to keep distance, it was kind a persecution

Would you find acceptable to send him a brief, honest message explaining how I felt and why I never said anything, without expecting anything in return? This is not my first option cause it's still humiliating. So i tried to edit a mp and leave it as an "easter egg" in his mp box (with me) in previous conversations. I am really struggling to let this go
I kinda gave this my time every day since January

Please no rude answer. I am not interfering in their relationship which by the way it's kinda not official yet
P.s.: i have a feelings she knew.