I've been using solid explorer for years now

mixplorer FTW

Mixplorer is the only answer

Mixplorer has absolutely never failed me over the past decade or so.

FX file explorer has been my main for years. Local/remote/ssh

It's not open source but it's quite literally the best Android application I've ever seen, by a significant margin. It's from the good old days where apps were small, very well designed, very polished and did not collect data.

It's FX, a gem ever more lost to time. The site is a bit old and unmaintained so SSL certificates may give you a bit of trouble, but you can just ignore the warnings, it's just an info page.

FX, despite not receiving updates for years has so many features of such great quality, I've yet to find any alternative with a truly competing interface and feature set.

Been using it for 10 years and it has been the pinnacle of Android.

Edit: I know you'll be detracted from trying it since it's not FOSS, but seriously give it a shot.

I use material files too cause its been suggested a lot in r/degoogle in reddit. But I'm not sure if its still maintained. Anyone has a better app which is also FOSS?

I've been using Amaze, it's nice, although I use it sparingly.
https://github.com/TeamAmaze/AmazeFileManager

Total Commander. For FOSS, Ghost Commander, similar but not exactly on par yet, at least in UX.

Mixplorer for sure

Another vote for FX File Manager, best file manager I've ever used on mobile

X-plore. Its the only one that lets you open multiple folders at once like you would on a desktop computer. It also is a built in FTP manager and will even replace your need to have separate cloud apps like Google Drive and Dropbox.

Filemanager +

Has everything I need, good UI, good quick access to commonly used folders and SD card, good file manipulation options.

I don't know which phone do you use, but I'm generally pretty satisfied with the default file managers which are preinstalled on Android devices (in my case, it's Samsung). Is there anything special you require from the file manager app which can't be done with the default one?

Material files. Seems to do the job for me.

https://play.google.com/store/apps/details?id=com.speedsoftware.explorer

This is my ride or die

Little File Explorer from F-Droid does for me the job.

The Material Files repo shows the last update was three weeks ago, but the latest version on the releases page and f-droid are from 2022. This is confusing...

Solid File Explorer, bought it forever ago, and it hasn't let me down yet.

FYI material files is maintained, there just hasn't been a release since may 2022. The last update was June 9 which you can see on the git repo https://github.com/zhanghai/MaterialFiles

any app from the 'Simple' suite is always worth checking out. (search 'simple files' on f-droid). i personally prefer the stock grapheneos one, but use Simple gallery