Short answer: Lync 2010/2013 are replaced by Skype for Business. Therefore you couldn´t any longer find them. But as Skype for Business also offered to manage the firmware for Lync Phones you should try that one (see here).
Keep noted that Lync 2010 already reached the end of the Mainstream Support as it was fully replaced by Lync 2013 (which is now replaced with Skype for Business; see below). Therefore Microsoft is pulling down the older evaluation versions (for example Lync 2010 which was here) as Lync 2010/2013 is already replaced with Skype for Business.
Note: Do not get confused with Lync Server and Lync client. There is still a Trial Lync client out there ( 32bit / 64bit ) BUT that's not the server.
For Lync 2013 its mostly the same, however its not that old but was already replaced with "Skype for Business". You could get such a evaluation version here, but that link no longer works due to the reason that there is now Skype for Business.
So the best option I think:
Would be the Skype for business evaluation version which you can get here.
I personally would directly start with Skype for Business. Its mostly identically to Lync 2013 and if you know Lync 2013 you could manage as well Skype for business.
Would be a MSDN subscription but what you can download here isn´t an evaluation version, its more a developer license to build something for Lync and test that. However for completeness I would like to mention it here as well. To lean what MSDN is start here.
I wouldn´t download Lync 2010/2013 from a non Microsoft Website (if you found one which host the old evaluation version for strange reasons; I also think its not legal to do that). The reason is that you couldn´t trust the source and might got something you do not really wish.