This is weird: Using the same operating system (Mint 20, lately – even though it’s out of date) my rendering times for the same sized files will vary wildly from day to day. Some days it renders very slowly and some days it’s not bad. Bizarrely, too, it seems to have nothing to do with any multi-tasking – other programs eating up processor and memory resources. It’s totally weird. At any rate you can do the following. Click the ‘ol “render” button and choose your options – format, where to save your file, etc. Then, at the bottom of the GUI click the thing that says something like “Generate Script. This will save a file at /home/username/Videos/kdenlive called something like “export.mlt”. You can call it whatever. Then, open that file in vim or nano – any text editor – and find the line that says real_time “-4” and change it to real_time “-1”. Then type:
melt export-1.mlt -progress
The progress flag has one hyphen before the word “progress”, to be clear. One comment under this video said that it worked well, for someone, changing the value described above to -2. You can experiment but -1 seemed to cut down render time by about 33-percent in my case.