Pharo 10 is a nice upgrade to Pharo 8, but is very new. You may try the following instructions that do get Seaside and the rest of the stack installed, but there may be unknown bugs.
Create a new Pharo 10 image in the Pharo launcher. Under official distributions, select Pharo 10.0 -64 bit. Give the image a shorter name: on Windows in particular there are problems with a path name getting too long. I suggest P10.
In the distribution, open a new Playground window and enter the following code
Transcript show:'Loading Voyage & Mongo';cr.
Metacello new
repository: 'github://pharo-nosql/voyage:pharo10-ready/mc';
baseline: #Voyage;
onConflictUseLoaded;
load.
Transcript show:'Loading Bootstrap & Seaside';cr.
Metacello new
repository: 'github://astares/Seaside-Bootstrap4:master/src';
baseline:'Bootstrap4';
onConflictUseLoaded;
load.
You will get two warning when you are installing Voyage. You can simply click the "Play" button to continue both times.
I have not been able to install one of the existing TinyBlog projects (yet) to verify that this works. Let me know if you can create a webpage succesfully!