These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.01 s (backtrack: 0/20).

[ebuild  N     ] net-libs/libnatpmp-20230423-r1::gentoo  26 KiB
[ebuild  N     ] net-libs/miniupnpc-2.3.3-r1:0/21::gentoo  USE="-verify-sig" 138 KiB
[ebuild  N     ] dev-cpp/nlohmann_json-3.12.0-r1::gentoo  USE="-test" 9452 KiB
[ebuild  N     ] net-misc/zerotier-1.16.0-r2::gentoo  USE="-controller -debug -sso" 11742 KiB

Total: 4 packages (4 new), Size of downloads: 21358 KiB