Not all Puppys are Ubuntu-binary compatible.
Over a dozen years ago, Puppy championed the use of self-contained applications you did not have to install: SFSes. Such applications require less than 1 Mb of RAM when linked to for ease of access but not opened; and when not mounted require no RAM and can not conflict with any other application available to the system.
A couple years ago the 'Big Boys' re-discovered that the Linux Kernel provided support for mounting file-systems. The first version of applications making use of that discovery were AppImages. As long as either the AppImage, itself, or the Puppy attempting to use it does, in fact, provide all dependencies, all you have to do is download an AppImage, make it executable and Left-Click to run it. It takes about 2 minutes to create a menu listing. Anyone can create AppImages and, indeed, fredx181 has published tool for that.
Flatpaks and Snapd came later. Flatpak was developed as part of the freedesktop.org project. Snap is a software packaging and deployment system developed by Canonical to compete with Flatpak. It is controlled by Canonical as are the repositories Snapd makes use of.
There is an application builtin to newer Puppys but available to all known as Pkg - CLI package manager https://oldforum.puppylinux.com/viewtop ... 31#p985531. Despite the term "CLI" in its name, it's installation provides two GUIs and it's 3rd way of being run --under a terminal-- is displayed as a menu system ala Winetricks. Like Apt-get, Pkg-CLI makes it easy to add repositories and install applications from them with dependency checking.
The Forum has a Specific Section for discussions about AppImages, Flatpaks and Snapd. viewforum.php?f=108. My recollection is that there have been reports of the successful installation and use of Flatpaks, but not Snapd. Something for you to explore via Pkg-Cli if you think its worth pursuing
But my guess is that others using Puppy have found no reason to add bloat to their system in order to make a Puppy more like a Ubuntu. The purpose of a computer operating system is to run applications and there are easier ways for Puppy to obtain the applications that Ubuntu has packaged as Snaps.
One of Puppys' objectives is to provide operating systems for older computers owned by those in regions where internet access may be spotty. The latest Ubuntu is a 2.7 Gb download, and to get it running your computer will need 2 GHz dual core processor or better, 4 GB system memory and 25 GB of free hard drive space. Jackalpup-slim is remaster of Fossapup64, binary compatible to Ubuntu Focal Fossa. It's a 662.3 Mb download, https://archive.org/details/Puppy_Linux_jackalpup which can serve as the base for using the applications most people want, and likely almost anything anyone would want. It's the base for puddleman's --its creator's-- jackalpup, a full music creator's studio. My guess --based on my recollection from using Fossapup--is that it requires less than 2 Gbs of RAM; and that fleshed out with whatever you want it will still fit on a 8 Gb USB-Stick with room to spare. If the computer it is to be run on can't support the kernel it's packaged with, a kernel-downgrade will require a less than 100 Mb download and take about 5 minutes to swap.
You've been here 5 days. When you've been here 5 years and mastered all the tricks Puppy has to offer, understand why Puppys are built as they are, and compared that to other systems, then come back and tell us why Puppy should be more like Ubuntu.
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EasyOS is a Puppy-variant, built to provide greater security. But in so doing, it sacrificed some of Puppy's ease of use and flexibility. None of the following --Antix, Porteus, Slax, Parrot, Kali, SystemRescue, Parted Magic-- offer a Puppy's flexibility and ease of use. DebianDogs do. But that's because they have been carefully designed with those objectives in mind. And there are still a couple of tricks up Puppys' sleeve not available to DebianDogs. For example, the ability to store settings, changes, and installed applications in a file mounted at boot-up from a USB-Key which is then unplugged and remains unplugged during a session.