The man himself who coined the term: Make a Joule thief.
I have a few projects using QX5252F (Djozz clock mod). It’s is similar to YX8018, which are typically used is outdoor solar lamps. I have couple running alkaline battery at sub lumen for a few months, and another running fairy lights at ultra low for almost a year.
I use rngwn 5mm these look better and have lower vf than cheap ‘cold white’ ones.