Not really. Even with modern technologies, the Linux desktop technology stack is very, very far behind when it comes to security.
The Linux kernel itself is a very weak foundation security-wise, the only way Android and ChromeOS get away with it is by using a very small feature set and restricting everything else as much as possible with seccomp, SELinux and heavy sandboxing.
The Linux desktop userland doesn't have meaningful hardening features compared to other platforms (even Windows is ahead, sadly). For example, practically all distros use glibc's memory allocator which has both poor performance and security [1] and their toolchain is based on gcc, with no support for modern compiler security features such as CFI (with the sole exception of Chimera Linux). Not to mention the permission model is completely outdated, like in that xkcd comic. Flatpak only mitigates this partially, because the Flatpak sandbox is very weak. The people working on Flatpak are doing their best, but from reading some GitHub issues, it's clear they are badly overworked and not security experts. The person responsible for Flatpak's seccomp sandbox has said it isn't even his main responsibility and he doesn't have much knowledge about seccomp and is learning along the way [2]. The Flatpak seccomp filter is based on a denylist rather than an allowlist, and many dangerous syscalls can't be blocked because applications rely on them (e.g. Firefox needs ptrace for the crash reporter). You also have to be very careful and use Flatseal (which is not officially supported) to deny permissions such as /home filesystem access, because it lets Flatpak apps override their own permissions by design [3]. And dangerous kernel components like io_uring are exposed [4], while Google disables them on their systems because of their exploitation potential.
The Linux kernel itself is a very weak foundation security-wise, the only way Android and ChromeOS get away with it is by using a very small feature set and restricting everything else as much as possible with seccomp, SELinux and heavy sandboxing.
The Linux desktop userland doesn't have meaningful hardening features compared to other platforms (even Windows is ahead, sadly). For example, practically all distros use glibc's memory allocator which has both poor performance and security [1] and their toolchain is based on gcc, with no support for modern compiler security features such as CFI (with the sole exception of Chimera Linux). Not to mention the permission model is completely outdated, like in that xkcd comic. Flatpak only mitigates this partially, because the Flatpak sandbox is very weak. The people working on Flatpak are doing their best, but from reading some GitHub issues, it's clear they are badly overworked and not security experts. The person responsible for Flatpak's seccomp sandbox has said it isn't even his main responsibility and he doesn't have much knowledge about seccomp and is learning along the way [2]. The Flatpak seccomp filter is based on a denylist rather than an allowlist, and many dangerous syscalls can't be blocked because applications rely on them (e.g. Firefox needs ptrace for the crash reporter). You also have to be very careful and use Flatseal (which is not officially supported) to deny permissions such as /home filesystem access, because it lets Flatpak apps override their own permissions by design [3]. And dangerous kernel components like io_uring are exposed [4], while Google disables them on their systems because of their exploitation potential.
Here is a more detailed article examining the lack of security of Linux phones in case you're interested: https://madaidans-insecurities.github.io/linux-phones.html
If you want a FOSS-based secure phone, GrapheneOS is the best option.
[1] Check this comment by GrapheneOS founder for some technical details and how it compares to hardened allocators such as Android's Scudo or Graphene's hardened_malloc: https://github.com/NixOS/nixpkgs/issues/90147#issuecomment-6...
[2] https://github.com/flatpak/flatpak/issues/4466#issuecomment-...
[3] https://github.com/flatpak/flatpak/issues/3637
[4] https://github.com/flatpak/flatpak/issues/5447