btop: [BUG] complains of no UTF-8 while locale *is* UTF-8

Describe the bug

Running on RHEL 7.7 at work, using the statically compiled binary 1.0.9, it complains of no UTF-8 locale detected. While locale is: [jdehaes@berx771 Snape]$ locale LANG=en_US.UTF-8 LC_CTYPE=“en_US.UTF-8” LC_NUMERIC=“en_US.UTF-8” LC_TIME=“en_US.UTF-8” LC_COLLATE=“en_US.UTF-8” LC_MONETARY=“en_US.UTF-8” LC_MESSAGES=“en_US.UTF-8” LC_PAPER=“en_US.UTF-8” LC_NAME=“en_US.UTF-8” LC_ADDRESS=“en_US.UTF-8” LC_TELEPHONE=“en_US.UTF-8” LC_MEASUREMENT=“en_US.UTF-8” LC_IDENTIFICATION=“en_US.UTF-8” LC_ALL=

When using the --utf-force flag, btop works perfectly. We have the same on other RHEL 7.x boxes. I can not compile/debug btop on this machine (as its compilers are too old - even with gcc 8.3 -std=c++20 is not available). On a RHEL 8 system this just works. I can compile/debug there (after installing gcc 10 toolchain), but useless as the problem doesn’t occur there. The locale settings are identical on that system.

To Reproduce

Get a RHEL 7.7 (probably any 7.x will do) system (via docker?) and copy the btop binary. It will complain although locale is UTF-8.

Expected behavior

btop can run with the --utf-force flag.

[jdehaes@berx771 Snape]$ btop ERROR: No UTF-8 locale detected! Use --utf-force argument to force start if you’re sure your terminal can handle it.

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Info (please complete the following information):

• btop++ version: 1.0.9
• Binary: static binary from release
• Architecture: x86_64
• Platform: Linux
• (Linux) Kernel: 3.10.0-1062.4.1.el7.x86_64
• Terminal used: mate-terminal
• Font used: Noto Mono for Powerline Regular

Additional context

contents of ~/.config/btop/btop.log -> nothing there other than no UTF-8 locale detected.