Mintupgrade to 21 requires for downgrading packages that 20.3 automatically set up to higher versions

No repository file, test, or entry point is named. Start by locating the mintupgrade code that assembles the apt downgrade command, then reproduce the PHP dependency failure and the subsequent Mint 20.3 upgrade; done means the upgrade path handles these package dependencies without the reported failure or unintended re-upgrade.

Hi everyone
It's somewhere though to understand if upgrading to 21 has been or not officially announced, but in any case if this can help developers, let me share my experience which leads me to give up for now the updgrade.

Mintupgrade requires the following packages to be downgraded:

DEBIAN_FRONTEND=noninteractive DEBIAN_PRIORITY=critical apt-get install --allow-downgrades -fyq -o Dpkg::Options::="--force-confold" -o Dpkg::Options::="--force-overwrite" libapache2-mod-php=2:7.4+75 libapache2-mod-php7.4=7.4.3-4ubuntu2.12 libargon2-1=0~20171227-0.2 libgd3=2.2.5-5.2ubuntu2.1 libgd3:i386=2.2.5-5.2ubuntu2.1 libidn2-0=2.2.0-2 libidn2-0:i386=2.2.0-2 libpcre16-3=2:8.39-12ubuntu0.1 libpcre2-16-0=10.34-7 libpcre2-16-0:i386=10.34-7 libpcre2-32-0=10.34-7 libpcre2-8-0=10.34-7 libpcre2-8-0:i386=10.34-7 libpcre2-dev=10.34-7 libpcre3=2:8.39-12ubuntu0.1 libpcre3-dev=2:8.39-12ubuntu0.1 libpcre32-3=2:8.39-12ubuntu0.1 libpcre3:i386=2:8.39-12ubuntu0.1 libpcrecpp0v5=2:8.39-12ubuntu0.1 libxml2=2.9.10+dfsg-5ubuntu0.20.04.4 libxml2:i386=2.9.10+dfsg-5ubuntu0.20.04.4 libzstd1=1.4.4+dfsg-3ubuntu0.1 libzstd1:i386=1.4.4+dfsg-3ubuntu0.1 ovmf=0~20191122.bd85bf54-2ubuntu3.3 php-apcu=5.1.18+4.0.11-1build1 php-bz2=2:7.4+75 php-common=2:75 php-curl=2:7.4+75 php-gd=2:7.4+75 php-imagick=3.4.4-4 php-intl=2:7.4+75 php-mbstring=2:7.4+75 php-mysql=2:7.4+75 php-xdebug=2.9.2+2.8.1+2.5.5-1build1 php-xml=2:7.4+75 php-zip=2:7.4+75 php7.4-cli=7.4.3-4ubuntu2.12 php7.4-common=7.4.3-4ubuntu2.12 php7.4-gd=7.4.3-4ubuntu2.12 php7.4-json=7.4.3-4ubuntu2.12 php7.4-mysql=7.4.3-4ubuntu2.12 php7.4-opcache=7.4.3-4ubuntu2.12 php7.4-readline=7.4.3-4ubuntu2.12 qemu-block-extra=1:4.2-3ubuntu6.23 qemu-efi-aarch64=0~20191122.bd85bf54-2ubuntu3.3 qemu-efi-arm=0~20191122.bd85bf54-2ubuntu3.3 qemu-system=1:4.2-3ubuntu6.23 qemu-system-arm=1:4.2-3ubuntu6.23 qemu-system-common=1:4.2-3ubuntu6.23 qemu-system-data=1:4.2-3ubuntu6.23 qemu-system-gui=1:4.2-3ubuntu6.23 qemu-system-mips=1:4.2-3ubuntu6.23 qemu-system-misc=1:4.2-3ubuntu6.23 qemu-system-ppc=1:4.2-3ubuntu6.23 qemu-system-s390x=1:4.2-3ubuntu6.23 qemu-system-sparc=1:4.2-3ubuntu6.23 qemu-system-x86=1:4.2-3ubuntu6.23 qemu-utils=1:4.2-3ubuntu6.23

but fails doing it by itself for anyone of them pretended as "broken" in this list

Reading package lists...
Building dependency tree...
Reading state information...
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 php-bz2 : Depends: php7.4-bz2 but it is not going to be installed
 php-curl : Depends: php7.4-curl but it is not going to be installed
 php-intl : Depends: php7.4-intl but it is not going to be installed
 php-mbstring : Depends: php7.4-mbstring but it is not going to be installed
 php-xml : Depends: php7.4-xml but it is not going to be installed
 php-zip : Depends: php7.4-zip but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

I began to try some investigation work to identify the guilty ones doing to downgrades manually.
Since any of the command lines sudo apt --fix-missing update nor the GUI tool is able to find some broken package, I tried yesterday evening the two first "libargon2-1" and "libgd3" then I gave up continuing this task for a good rest.

And guess what I see this morning? That the mint 20.3 update tool has detected the need to upgrade back again these two previously downgraded packages which demonstrates that their installation was not due to an intentional action on myself.

So what to conclude about this mintupgrade tool ? Is it ready or too soon and buggy and we should be waiting for a next release ?